Configure Iredmail server to add Envelope-to: header

I need a change made to Iredmail server to add an envelope-to: header. that will contain the email address that sending mailserver sent the mail to. This needs to be accurate even if Iredmail actually delivered to a different address than the to: header. For example: If delivered via a catchall account. If original email has a missing to: header If original email was delivered using a bcc. We currently use a hosted solution from hostgator, the uses EXIM as the MTA, which works perfectly. However Iredmail appears to use postfix as the MTA, and does not appear to add a envelope-to: header. See also: [login to view URL] this seems to be similar to what we are trying to accomplish, but it does not work, likely because it is for an older version of iredmail.